RaptorJS – An End-to-End JavaScript Toolkit for Building Adaptive Modules and UI Components

RaptorJS is an open-source toolkit for building JavaScript modules and UI components that function on the server and in the browser. RaptorJS promotes modularity, which is crucial to building reasonably complex HTML web applications that are maintainable, easily testable, and optimized. The central goal of RaptorJS is to enable applications to provide the best user experience.

As an eBay project, RaptorJS was designed to be extremely efficient and lightweight. Rather than being a monolithic framework, RaptorJS embraces a modular design; it is intended to work alongside existing JavaScript libraries—not replace them.

RaptorJS provides support for the following features:

  • Object-oriented JavaScript: Defining JavaScript modules, classes, mixins, and enums based on the Asynchronous Module Definition (AMD) syntax
  • Resource optimization: Resource minification, bundling, compilation, checksums, and CDN integration for optimal delivery of JavaScript modules and UI components to the browser
  • Packaging: Defining dependencies for JavaScript modules and UI components based on simple package.json files, with support for optional and environment-specific dependencies
  • Client-side asynchronous package loading: Downloading packages of JavaScript and CSS resources asynchronously after the initial page load
  • Server-side JavaScript module loading: Loading JavaScript modules in multiple server-side JavaScript environments, including Node and Rhino
  • HTML templating: Using the same extensible templating language on both the server and in the browser to build UI components and web pages
  • Widgets: Automatic binding of JavaScript behavior to DOM nodes associated with rendered UI components—whether the UI component was rendered on the server or in the browser

The following sections describe each of these features in more detail.

Object-oriented JavaScript

Using the RaptorJS library, you can define namespaced modules, classes, mixins, and enums. This library employs a clean and easy-to-understand syntax based on the AMD syntax.

To make building modular JavaScript applications even easier, RaptorJS provides an AMD implementation that extends AMD in backwards-compatible ways. The syntax is very close to pure JavaScript, but fills gaps in the existing JavaScript language. Now you can start creating modular code that is easy to maintain without waiting for a new version of JavaScript or switching to an alternative language.

Resource optimization

The RaptorJS Optimizer is a server-side tool to build optimized web pages by bundling, compiling, and minifying page dependencies. This tool makes managing complex JavaScript and CSS dependencies almost effortless while helping you produce extremely optimized web pages.

Unlike other optimizers, the RaptorJS Optimizer does not require that you write your code a certain way. Simply tell the optimizer which modules your page depends on, and it will take care of the rest—including writing optimized JavaScript and CSS bundles to disk and generating the HTML that is required to include those bundles. Since every application has different requirements, the RaptorJS Optimizer gives you full control over how resources are combined and where to include resources on your HTML pages.

All dependencies are described using RaptorJS package.json files, which are easy to maintain and allow you to leverage the full power of the RaptorJS Packaging system.


RaptorJS extends the popular package.json format so that it is better suited for packaging up JavaScript modules and UI components to be delivered to the browser. RaptorJS packages are used by the RaptorJS server-side module loader, as well as to optimally deliver only the required code to the browser. RaptorJS imposes no requirements on the code that is packaged, so you can continue to write code however you prefer. Furthermore, RaptorJS packages are extensible and support any type of dependencies (JavaScript, CSS, LESS, Raptor Templates, etc.).

Here are some of the use cases this packaging model supports:

  • You can create separate RaptorJS packages for JavaScript modules and UI components.
  • JavaScript modules and UI components can be delivered and loaded differently based on the target environment. For example, you can package UI components so that CSS code sent to mobile devices is different from the CSS code sent to desktop browsers.
  • You can make dependencies explicit—including which dependencies are optional or environment-specific.

Client-side asynchronous package loading

RaptorJS includes a lightweight AMD-compatible package/module loader that enables JavaScript and CSS resources to be downloaded asynchronously after the initial page load. This asynchronous package loader works in conjunction with the RaptorJS Optimizer to efficiently download resources from the server.

Server-side JavaScript module loading

RaptorJS provides a server-side module loader that integrates with multiple server-side JavaScript environments, including Node and Rhino. The server-side module loader reads modules’ package files to determine which code to load based on the target environment.

The RaptorJS AMD module loader integrates seamlessly with the Node module loader. In addition, RaptorJS provides a fully compliant CommonJS and AMD module loader for Rhino.

You can load JavaScript modules in multiple server-side JavaScript environments, and you can load JavaScript modules differently in Node and Rhino server-side JavaScript environments.

HTML templating

Raptor Templates is a new templating language that elegantly blends powerful templating directives with HTML tags. Unlike most other templating languages, Raptor Templates also enables you to use custom tags to embed high-level UI components into templates.

Raptor Templates is XML-based so that the XML structure of an HTML document can be used to its full advantage, making it simpler for you to write easily readable templates and to provide optimal output. Raptor Templates includes a compiler that converts HTML templates into native and optimized JavaScript code. Equally effective in both the browser and on the server, no other templating language makes it so effortless to produce easily readable templates that are blazingly fast with such a miniscule footprint.

Use Raptor Templates wherever you want to produce HTML.


The RaptorJS Widget Framework simplifies the creation of web applications built using UI components. This lightweight framework provides a mechanism for automatically attaching JavaScript behavior to the DOM subtrees associated with rendered UI components—regardless of whether the UI components were rendered on the server or in the web browser.

The RaptorJS Widget Framework does not dictate how a client-side widget is implemented. Furthermore, there is no complex class inheritance hierarchy (only a few mixins that get applied to all initialized widgets).

UI components that use Raptor Templates to render their view will benefit from the bindings that allow widgets to be attached to rendered HTML elements. During the rendering of an HTML template, the widget framework keeps track of which widgets have been rendered and which HTML element each widget is bound to. As a result, widgets can be automatically and efficiently initialized without having to rely on the CPU-intensive task of scanning the final DOM tree to discover rendered widgets.


Lightweight, optimized, modular, portable, and designed for scale, RaptorJS simply makes JavaScript better. To view demos and get started, visit http://raptorjs.org.

Kudos to Patrick Steele-Idem (@psteeleidem) of eBay’s presentation platform team, who built RaptorJS.

— Neeraj Khanna (@nk94555), presentation engineer at eBay